The present invention relates to the packaging of integrated circuits (ICs) and more particularly to a method of forming a flip-chip, bump carrier type package.
Modern consumer electronics, such as cellular phones, digital cameras, and digital music players are driving a demand for smaller integrated circuits. Thus, semiconductor manufacturers and packaging companies are continually shrinking the footprint of packaged electronic devices yet at the same time increasing circuit functionality. One way of reducing package size is to use a bumped die and electrically connect the die to a substrate or carrier in a face-down manner. This is known as flip-chip assembly because the chip is face down or flipped, as compared to wire-bonding technology, where the chip is face-up and wires are connected between bond pads on the top of the chip and the carrier to which the bottom of the chip is attached. Although flip-chip technology is not new, it is just now becoming increasingly popular.
FIG. 1 shows a packaged device 10 in which a semiconductor die 12 is electrically connected to stud bumps 14 with wires 16. The wires 16 extend from a top of the die 12 to the stud bumps 14. A plastic material 18 covers the wires and the top of the die 10 for protection. FIG. 2 shows a packaged device 20 in which a semiconductor die 22 is electrically connected to a carrier or substrate 24 with bumps 26. An underfill material 28 is disposed between the die 22 and the carrier 24. Solder balls 30 are attached to an opposing side of the carrier 24 to provide electrical connection to other electronic devices. A plastic material 32, indicated with dashed lines, is formed around the die 22 to complete the package 20.
The packaging process can be very complex due to the varying compositions of the materials, like the carrier, the die, the solder balls and the mold compound. Problems caused by excessive heat and tight tolerances are often encountered. For example, the solder balls 30 sometimes fall off or disengage from the carrier 24. It would be advantageous to provide a method of making a reliable flip-chip packaged device.